Should the design pressure of the GC1 pipeline be higher than the discharge pressure at which the safety valve activates?
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I would like to ask everyone: Both the 2020 and 2016 versions of GB20801.3 specify that \"the pressure and temperature of GC1-class pipelines must not exceed the design limits.\" The 2020 version is 4.2.3.2 ； The 2016 version is the first sentence of 4.2.3. Should the pipe pressure and temperature described here include values corresponding to the safety valve discharge condition? If the set pressure at which the safety valve operates is close to the upper limit specified for the pipeline grade, such as PN63 for pipes made of material 20 with A105 flanges, and the set pressure of the safety valve on that pipe is 6.1 MPa, then the design pressure of the pipe is also set at 6.1 MPa. If it is taken into account that the pressure under the relief valve’s discharge condition should be lower than the design pressure of the pipeline, then the design pressure of the pipeline must be determined based on the relief valve’s discharge pressure: 6.1*1.21=7.381 MPa. As a result, the entire piping system will need to be upgraded from PN63 to PN110. Although we don’t usually use such extreme design approaches, I still would like to ask everyone: when designing pipelines, does the pressure need to take into account the discharge pressure of the safety valve?
I have come across safety valve data sheets from many large design institutes, and most of them do not take this into account. The setting pressure of the safety valve is the same as the design pressure of the pipeline.
Thank you. We have always done it this way before, but this requirement in GB20801 is really a bit confusing.
But I personally think this design is unreasonable, because when the safety valve releases pressure, it can sometimes take up to half a minute to do so. This creates a security risk.
But as you said, the pressure level of the entire piping system needs to be increased by one stage, which raises the cost of the entire piping system.
There’s no need to worry about these; the activation of the safety valve always indicates abnormal operating conditions
The setting pressure of safety valves is generally determined based on the design pressure that the equipment can withstand. Under normal conditions, the pressure that pipes can withstand is much higher than that which the equipment can handle.
Experts passing by, please give some advice
Under normal circumstances, the two are indeed quite far apart; this is a special situation now, as the design pressure of the pipeline is right at the limit.:)
When the safety valve opens, the film stress resulting from the applied pressure should not exceed 0.9 times the yield strength at that temperature; this is stipulated in B31.3. The core content of domestic standards is actually derived from B31.3 as a whole, especially GB20801; therefore, it is appropriate to follow this requirement.